The present invention relates to devices and methods for obtaining samples of blood and other fluids from the body for analysis or processing.
Many medical procedures in use today require a relatively small sample of blood, in the range of 5-50 xcexcL. It is more cost effective and less traumatic to the patient to obtain such a sample by lancing or piercing the skin at a selected location, such as the finger, to enable the collection of 1 or 2 drops of blood, than by using a phlebotomist to draw a tube of venous blood. With the advent of home use tests such as self monitoring of blood glucose, there is a requirement for a simple procedure which can be performed in any setting by a person needing to test.
Lancets in conventional use generally have a rigid body and a sterile needle which protrudes from one end. The lancet may be used to pierce the skin, thereby enabling the collection of a blood sample from the opening created. The blood is transferred to a test device or collection device. Blood is most commonly taken from the fingertips, where the supply is generally excellent. However, the nerve density in this region causes significant pain in many patients. Sampling of alternate site, such as earlobes and limbs, is sometimes practiced to access sites which are less sensitive. These sites are also less likely to provide excellent blood samples and make blood transfer directly to test devices difficult.
Repeated lancing in limited surface areas (such as fingertips) results in callous formation. This leads to increased difficulty in drawing blood and increased pain.
To reduce the anxiety of piercing the skin and the associated pain, many spring loaded devices have been developed. The following two patents are representative of the devices which were developed in the 1980s for use with home diagnostic test products.
U.S. Pat. No. 4,503,856, Cornell et al., describes a spring loaded lancet injector. The reusable device interfaces with a disposable lancet. The lancet holder may be latched in a retracted position. When the user contacts a release, a spring causes the lancet to pierce the skin at high speed and then retract. The speed is important to reduce the pain associated with the puncture.
U.S. Pat. No. 4,517,978, Levin et al., describes a blood sampling instrument. This device, which is also spring loaded, uses a standard disposable lancet. The design enables easy and accurate positioning against a fingertip so the impact site can be readily determined. After the lancet pierces the skin, a bounce back spring retracts the lancet to a safe position within the device.
In institutional settings, it is often desirable to collect the sample from the patient and then introduce the sample to a test device in a controlled fashion. Some blood glucose monitoring systems, for example, require that the blood sample be applied to a test device which is in contact with a test instrument. In such situations, bringing the finger of a patient directly to the test device poses some risk of contamination from blood of a previous patient. With such systems, particularly in hospital settings, it is common to lance a patient, collect a sample in a micropipette via capillary action and then deliver the sample from the pipette to the test device.
U.S. Pat. No. 4,920,977, Haynes, describes a blood collection assembly with lancet and microcollection tube. This device incorporates a lancet and collection container in a single device. The lancing and collecting are two separate activities, but the device is a convenient single disposable unit for situations when sample collection prior to use is desirable. Similar devices are disclosed in Sarrine, U.S. Pat. No. 4,360,016, and O""Brien, U.S. Pat. No. 4,9249,879.
U.S. Pat. Nos. 4,850,973 and 4,858,607, Jordan et al., disclose a combination device which may be alternatively used as a syringe-type injection device and a lancing device with disposable solid needle lancet, depending on configuration.
U.S. Pat. No. 5,318,584, Lange et al., describes a blood lancet device for withdrawing blood for diagnostic purposes. This invention uses a rotary/sliding transmission system to reduce the pain of lancing. The puncture depth is easily and precisely adjustable by the user.
Suzuki et al., U.S. Pat. No. 5,368,047, Dombrowski, U.S. Pat. No. 4,654,513 and Ishibashi et al., U.S. Pat. No. 5,320,607, all describe suction-type blood samplers. These devices develop suction between the lancing site and the end of the device when the lancet holding mechanism withdraws after piercing the skin. A flexible gasket around the end of the device helps seal the end around the puncture site until adequate sample is drawn from the puncture site or the user pulls back on the device.
U.S. Pat. No. 4,637,403, Garcia et al, and U.S. Pat. No. 5,217,480, Haber et al, disclose combination lancing and blood collection devices which use a diaphragm to create a vacuum over the wound site.
International Application Publication Number WO 95/10223, Erickson et al, describes a means of collecting and measuring body fluids. This system uses a disposable lancing and suction device with a spacer member which compresses the skin around the lance/needle.
Single use devices have also been developed for single use tests, i.e. home cholesterol testing, and for institutional use to eliminate cross-patient contamination multi-patient use. Crossman et al, U.S. Pat. No. 4,869,249, and Swierczek, U.S. Pat. No. 5,402,798, also disclose disposable, single use lancing devices.
Even with the many improvements which have been made, the pain associated with lancing remains a significant issue for many patients. The need for blood sampling and the fear of the associated pain is also a major obstacle for the millions of diagnosed diabetics, who do not adequately monitor their blood glucose due to the pain involved. Moreover, lancing to obtain a blood sample for other diagnostic applications is becoming more commonplace, and a less painful, minimally invasive device is needed to enhance those applications and make those technologies more acceptable.
An object of the present invention is to provide a device and a method for obtaining a sample of bodily fluid through the skin which is virtually pain free and minimally invasive.
Another object of this invention is to provide a method which can result in a sample of either blood or interstitial fluid, depending on the sample site and the penetration depth utilized. While there are no commercially available devices utilizing interstitial fluid (ISF) at this time, there are active efforts to establish the correlation of analytes, such as glucose, in ISF compared to whole blood. If ISF could be readily obtained and correlation is established, ISF may be preferable as a sample since there is no interference of red blood cells or hematocrit adjustment required.
Another object of this invention is to provide a method which can draw a small but adjustable sample, i.e. 3 xcexcL for one test device and 8 xcexcL for another test device, as appropriate.
Another object of this invention is to provide a method by which the drawn sample is collected and may be easily presented to a testing device, regardless of the location of the sample site on the body. This approach helps with infection control in that multiple patients are not brought in contact with a single test instrument; only the sampling device with a disposable patient-contact portion is brought to the test instrument. Alternatively, the disposable portion of a test device may be physically coupled with the sampler so the sample can be brought directly into the test device during sampling. The test device may then be read in a test instrument if appropriate or the testing system can be integrated into the sampler and the test device can provide direct results displayed for the patient.
It is a further object of the invention is to provide a device for minimally invasive sampling comprising a reusable sampler and disposable sample collection.
In one aspect, the present invention relates to a device which uses mechanical motion to pierce the skin, and a mechanical kneading or oscillation to produce a sample of fluid from the body and may employ a back pressure or vacuum to collect a small fluid sample into the device. More specifically, the present invention comprises a reusable sampling device and a disposable piercing/collecting apparatus. The device may also employ a back pressure, capillary or vacuum to collect a small fluid sample into the piercing/collecting apparatus that may later be discharged to deliver the collected sample to a test device or other appropriate vessel. The system may alternately be used to deliver the sample to an integral disposable test device, without collecting and separately dispensing the body fluid sample.
A method aspect of this invention involves piercing of the skin at a rapid rate (to minimize pain), with a needle (which minimizes the trauma and pressure-associated pain response which occurs with a traditional lancet). The skin is kept taut during the lancing to allow accurate and repeatable penetration of the needle into the skin. After piercing the skin, the needle is withdrawn from the wound and the surrounding area kneaded by ultrasonic action, piezoelectric or mechanical oscillation or squeegee motion to stimulate the blood flow into and from the wound. Additionally heat, electrical potential or friction can be used to stimulate additional flow of the body fluid. This fluid or blood flow can also be stimulated by ultrasonic vibration of the skin surrounding the wound. In an alternate embodiment to stimulate blood flow, the needle remains in the wound for a period of time, with either slow mechanical vibration or rotation of the needle, ultrasonic, or piezoelectric oscillation of the needle, to keep the wound open for blood to pool. After the area has been stimulated and the blood wells up in the wound, a capillary, syringe or pumping system is used to draw microliter samples from the patient. Suction is applied to the needle or the suction tube through either peristalsis, convection (application of heat to a capillary tube) or by the piston of a small microsyringe. The piston is pulled back into the sampler device with spring action, generating a vacuum in the barrel of the microsyringe and quickly drawing fluid from the body through the needle or the suction tube into the barrel to normalize the pressure differential. The piston or suction device then can be reversed to dispense the collected sample. The system can also use a capillary tube which is used to draw the sample after it has been collected on the skin surface. The capillary tube can then dispense the sample to a desired test or analysis device by applying pressure through the tube or simply contacting the end of the tube and the sample with a surface or material that has sufficient affinity for the fluid to pull the sample from the tube.
The above method and system may be used on various parts of the body. It is particularly appropriate for use on sites other than the fingertips. Although fingertips provide good blood flow, the high density of pain receptors provide for easy access to blood but maximum pain in sampling. The method of this invention actively draws a sample from the body, enabling the use of sampling sites on the body which are inadequate for traditional lancing. Since the method can also provide a mechanism for the easy transfer of the sample, the difficulty of bringing the sample to a test device is eliminated. An important benefit of this system is that the use of alternate sites on the body reduces the accompanying pain sensation and encourages more frequent use as needed.
While the method may be readily used to obtain a blood sample in a minimally invasive fashion, a sample of interstitial fluid may similarly be obtained, generally utilizing a less deep puncture in sites with lower blood flow. This will become more important as tests are developed which can utilize ISF samples, which may be preferred compared to blood.
This invention provides a device and method for lancing a patient and virtually simultaneously producing and collecting the fluid sample, which may be transferred to a test device. A preferred device of the present invention comprises a blood collection system including a lancing needle, drive mechanism, kneading or vibration mechanism and optional suction system and sample ejection mechanism. The device is preferably sized to be hand-held in one hand and operable with one hand. The device can optionally contain integral testing or analysis component for receiving the sample and providing testing or analysis indication or readout for the user.
The lancing needle and firing mechanism designed to create a wound which will both provide an adequate sample but which will still close and heal quickly. Wound healing is an especially important consideration for diabetic patients who often have compromised circulatory systems and slow healing processes. The wound must have a geometry which allows for a momentary space in which blood can fill, taking into account the elastic nature of the skin tissues. Careful consideration must be given to these geometries or the dermis will seal around the lancing needle tip, precluding the drawing of a sample through the tip. In a preferred embodiment a needle is used in combination with a flexible collar and outer tube to spread the wound so blood can pool. Alternatively a multiple needle lancing device can be used to generate a wound which disrupts multiple capillary areas to quickly provide large sample size, but the smaller multiple wounds, can heal more easily.
In an alternate embodiment, the needle/lance is withdrawn from the wound, and the area surrounding the wound is massaged or stimulated to prevent it from closing and to promote the flow of body fluids and or blood to the wound and to the surface of the skin.
Devices according to this invention create a lancing motion which cuts into the small but plentiful capillaries in the superficial vascular plexus under the epidermis. This vascularized region starts at a depth of 0.3-0.6 mm from the surface of the skin in many accessible areas throughout the body (forearm, thigh, abdomen, palm). Blood is in plentiful supply in this region of the skin, and healing of small wounds is not problematic. However, bringing a sizable drop of blood to the surface is more problematic than with a finger stick. A finger stick is typically massaged to increase momentary blood flow. This invention provides a system for mechanically massaging a lance site at other body locations by several different approaches, including oscillating an annular ring surrounding the wound to pump the blood surrounding the wound into the wound for extraction by a needle or capillary tube or oscillating paddles or other members adjacent the wound to achieve the desired blood flow. Further, bringing a drop of blood from the skin in other regions of the body, e.g., the thigh, to a small area on a test device is very difficult. An alternate embodiment of the present invention works with the needle remaining in the wound and the needle being mechanically manipulated to promote the formation of a sample of body fluid in the wound.
The needle may be vibrated in any desired and effective motion, including an up and down motion, a side to side motion, a circular motion, a rotation motion or any combination thereof. This creates a momentary opening in which the blood can fill while the device draws the blood through the needle into the disposable sample collection chamber. The vibration of the needle may occur across a broad range, from 30 cycles per minute up to 1000 cycles per minute or more. This slight vibration does not measurably increase the sensation felt by the patient, particularly when a short duration time is used, but does markedly increase the sample volume which may be easily withdrawn from a given wound and the rate at which the sample volume is produced from the wound. The oscillation can cause the needle to move up to 2-3 mm per cycle. The optimal needle oscillation is less than 1.5 mm, with about 0.5 mm preferred based on current investigations. Oscillating or rotating the needle from 30 cycles per minute up to 1000 cycles per minute or more holds the wound open and prevents it from closing and stopping sample collection and provides sample collection in a shorter amount of time.
Lancing conventionally occurs at a 90 degree angle (perpendicular) to the skin surface. However, we have found that the lancing member may puncture significantly more capillaries if the lancing is performed on a angle. At a too shallow angle, no significant depth of penetration is achieved. Lancing at an incident angle of 15-90 degrees to the surface of the skin is effective, with shallower angles producing greater blood flow.
The device and system of this invention can further enhance blood flow by massaging the site prior to lancing, as well as by massaging the area adjacent the lancing cite while the lancing member is in the wound and after it is removed from the wound, as well as during sample collection, as described above. Alternate methods can use a wiper to rub across or vibrate the skin or can apply heat to the skin to increase the blood flow to the sampling site.
In another alternate configuration, the lancing needle may be withdrawn very slightly from the point of maximum penetration to create an opening in which blood can pool before being suctioned through the device. This can be accomplished with a double stop system which stops the needle at maximum penetration then stops the retraction of the needle at partial but not full retraction. The area surrounding the wound can be kneaded or massaged by optional movable members mechanical to stimulate blood flow to the wound and increase the sample size and the rate of production of the sample. The mechanical motion can displace the area around the wound from 0.05 to 8 mm, with 1-5 mm being preferred based on current investigations. A wiper device can be used in the aspect which rubs the skin to increase the blood flow to the wound by stimulating the capillaries.
The mechanical stimulation of the wound can be accomplished by different methods or motions and members. An annular ring or other polygon or blade or paddle members may be oscillated around the wound by piezoelectric, ultrasonic, solenoid/coil, motor and cam or other methods apparent to one skilled in the art. Mechanical oscillation in the range of 2 to 1000 cycles per minute may be employed, with 10 to 400 cycles being preferred. Ultrasonic vibration has been effective at a frequency as high as 40 kHz. Alternately, the device may employ a blade or squeegee type of stimulator which kneads the site with horizontal or a combination of horizontal and vertical action and promotes blood flow to the wound. The squeegee may act on the wound area 2 to 200 times per minute, with 60 times per minute preferred based on current investigations. Additionally, the needle may be vibrated ultrasonically, with or without the kneading or massaging action adjacent the wound. The ultrasonic vibration can cover the range of ultrasonic frequencies depending on the sampling area and whether the needle or the stimulation device is being activated.
In another aspect of this invention the lancing member is contained a multi-chambered or multi-channelled capillary disposable member wherein one chamber contains the lancing member and an adjacent chamber is adapted to receive the blood or fluid exiting the wound. The multi-chambered capillary disposable can be made from any suitable material, and installed in the sampler so that it is positioned in the appropriate position relative to the wound created to permit collection of the sample. The lancing device is driven into the skin and withdrawn by the secondary retraction springs after reaching the limit stops. After withdrawal of the lancing member, the stimulator ring or other polygon shape is oscillated by one of the various methods to pump blood from the capillaries adjacent to the wound. The sampling device of this aspect of the invention has stop mechanisms to limit the penetration of the lancing member and sample duration system which sets the time of the sample collection. The lancing guide chamber can be formed a variety of ways and one skilled in the art can reconfigure it to create alternate embodiments.
In another aspect similar to the above, the lancing member can be contained within a single capillary tube and adapted to extend from the end of the tube to create the wound. The lancing member then retracts a sufficient distance inside the capillary to allow the desired sample to be collection in the end of the same capillary tube in the space below the retracted lancing member. In such an embodiment the lancing member can be vibrated in the wound before retraction, also as described above.
To achieve the sample collection after withdrawing the needle, a stimulator ring can be used to pump the sample from the surrounding capillaries through the wound opening. The stimulator ring is designed to keep the skin taut to allow better penetration of the skin during lancing and help keep the wound open during pumping. It can be oscillated appropriately to insure that enough sample is pumped from the local capillaries. The time or number of cycles varies by individual and location being sampled. To achieve a variable sample time either of the following methods may be used. A sensor can be built into the sampler which senses the blood in the collection chamber or device. When an adequate sample level (which may be adjustable) is reached, the stimulation mechanism is turned off. A second method is to have a patient definable input which sets the time duration for the test or the number of cycles for the stimulation ring. Additional stimulator motions can be employed to promote the extraction of bodily fluids. These include sinusoidal motion, wobbling, kneading or peristaltic motion. An alternate stimulator device can be designed with an inner and outer ring which will alternate creating a peristaltic pumping motion on the capillaries surrounding the wound. Another alternate stimulator device uses a spiral spring that can be compressed flat to emulate multiple pumping rings. As will be apparent, various configurations of multiple stimulator rings, paddles, or other members, used in various rhythms and orders of movement can be employed in the present invention. The stimulator ring or member can be heated in order to heat the skin to increase the capillary volume flow to and out of the wound. In addition, the housing or case of the device or other components of the device can be heated to provide heating of the skin.
In another aspect of the invention a diffused laser may be used to penetrated to the superficial vascular plexus and a capillary tube may be used to collect the sample. A lens may be used to diffuse the laser so that it does not create a large wound or damage large areas of skin and tissue. A minimum wound size is important to enable rapid healing. The capillary collection tube can use a suction generator to draw the sample up the tube and can also utilize an optional stimulator ring to pump the blood from the adjacent capillary beds.
In another aspect of the invention the lancing can be accomplished by a pulse of a fluid under high pressure such as a liquid or a compressed gas. In addition the compressed gas can be directed, at lower pressure, to the skin surface to massage the skin before lancing, during lancing and/or during sample collection. Pulsing the compressed gas against the skin at desired pressures, patterns and intervals, including sequential pattern across the surface of the skin, can provide the desired stimulation of the blood flow into and from the wound. The pulse of compressed gas used to perform the lancing and opening of the wound can be a single pulse or multiple pulses, can be directed through a capillary sample collection tube, and/or can be applied vertically to the skin surface or at an angle, as described above for other lancing members, to achieve puncturing the maximum capillaries in the skin and provide the sample collection in a short period of time.
In another aspect of the invention an off meter test device is used with a sampler of this invention to provide an integrated sampling and testing device. This device can be used by the patient to essentially simultaneously draw a sample and test for the presence or concentration of an analyte in a body fluid. The sample can be taken from an alternate location other than the fingertips with the device of this invention. To accomplish this it is critical to the test to provide a mechanism to stimulate the wound and or the surrounding area to provide an adequate sample for the test device. This stimulation can be accomplished by manipulating the needle or the area of skin surrounding the wound as described above. A combination of the two methods can be employed to increase the volume and/or decrease the sampling time. The sample is introduced directly into a test device or testing area rather than being collected and subsequently dispensed.
In another aspect, this invention also provides a method of determining the correct sample size prior to transferring or testing. Different methods can be used to sense the volume and/or presence of the sample. One system uses two contacts to sense the presence and/or volume of a sample. The body fluid either is drawn up a tube or wells up on the surface of the skin where it creates a short between two contacts which signal that the proper sample has been drawn. An alternate system uses an LED and receiver. When the sample rises to the level where it blocks the LED from the receiver the proper sample has been drawn. Other optically activated or contact activated systems can be used in this aspect of the invention.
In another aspect, this invention also provides a method of making a unit with a disposable section to limit biohazard cross contamination.
In another aspect, this invention provides a bell shape capillary tube. The capillary tube wicks the sample up the tube until it reaches the transition of the bulb. The bulb is then depressed to expel the sample or a known volume of the sample to a desired location, such as a test strip or device for analysis. The bell shape can be designed as a cone and the sample is wicked up the cone and dispensed by reversing the cone and expelling the sample by capillary action onto the test device.
In an alternate embodiment the device of this invention lances and stimulates the area, creating a drop of sample fluid, which is collected on or transferred directly to a test device by applying the test device to the drop.
In another aspect, this invention can also include an auto-injection device. A preloaded tip may be placed into the barrel. The trigger and spring system can be designed to deliver the sample from the syringe rather than to collect a sample into the syringe. One who is skilled in the art could readily reconfigure the mechanism described to inject a sample. Moreover, the device may have dual function of collecting a sample while simultaneously or sequentially injecting a sample, which can be in response to a test performed in the device on the sample collected.